Automobile emissions are said to be the single greatest source of pollution in several cities across the country. Automobiles emit hydrocarbons, nitrogen oxides, carbon monoxide and carbon dioxide as a result of the combustion process. The Clean Air Act of 1970 and the 1990 Clean Air Act set national goals of clean and healthy air for all and established responsibilities for industry to reduce emissions from vehicles and other pollution sources. Standards set by the 1990 law limit automobile emissions to 0.25 grams per mile (gpm) nonmethane hydrocarbons and 0.4 gpm nitrogen oxides. The standards are predicted to be further reduced by half in the year 2004.
It is expected that automobiles will continue to be powered by internal combustion engines for decades to come. As the world population continues to grow, and standards of living continue to rise, there will be an even greater demand for automobiles. The increasing number of automobiles is likely to cause a proportionate increase in pollution. The major challenge facing automobile manufacturers is to further reduce undesirable and harmful emissions by improving fuel economy, thereby assuring the increased number of automobiles has a minimal impact on the environment. One method by which automobile manufacturers have attempted to improve fuel economy and reduce undesirable emissions is cylinder deactivation.
Generally, cylinder deactivation is the deactivation of the intake and/or exhaust valves of a cylinder or cylinders during at least a portion of the combustion process thereby reducing pumping work, and is a proven method by which fuel economy can be improved. In effect, cylinder deactivation reduces the number of engine cylinders within which the combustion process is taking place. With fewer cylinders performing combustion, fuel efficiency is increased. For example, in an eight-cylinder engine under certain operating conditions, four of the eight cylinders can be deactivated. Thus, combustion would be taking place in only four, rather than in all eight, cylinders. Cylinder deactivation is effective, for example, during part-load conditions when full engine power is not required for smooth and efficient engine operation. Studies have shown that cylinder deactivation can improve fuel economy by as much as fifteen percent.
Conventional methods of achieving cylinder deactivation, however, have generally been accomplished by the addition of numerous component parts to various portions of the valve train. These additional component parts, such as, for example, multiple springs, arm members, shaft members, and pins, have typically not fit within the space occupied by conventional drive train components. Thus, the conventional methods of implementing cylinder deactivation have required modification and redesign of valve trains and engines to provide the additional space within which to house the additional components used to achieve cylinder deactivation. Furthermore, conventional devices used to achieve cylinder deactivation are typically moderately complex mechanical devices assembled from numerous subassemblies and component parts. The assembly of a device from numerous component parts requires significant labor and the need to inventory and maintain a supply of the various component parts, thereby increasing the cost of manufacture. Moreover, the numerous component parts used in a conventional cylinder deactivation device contribute mass to the device, may impact the reliability of the device, and may limit the performance of the device to certain engine operating ranges.
Therefore, what is needed in the art is a cylinder deactivation device which is designed to fit within existing space occupied by conventional drive train components, thereby avoiding the need to redesign such engines and their valve trains.
Furthermore, what is needed in the art is a cylinder deactivation device that is relatively simple and uses a minimum of component parts, and is therefore manufactured in a cost-effective manner.
Yet further, what is needed in the art is a cylinder deactivation device having a low mass that is capable of operating over a substantial range of engine operating parameters.